Effect of composition of starting materials of Mo–Si on self-propagating high temperature SHS reaction

Abstract

An experimental study of the self-propagating high temperature synthesis of Mo–Si alloys was conducted from elemental powder compacts. Test specimens with seven compositions, including Mo/Si = 1∶1·25, 1∶1·50, 1∶1·75, 1∶2·00, 1∶2·25, 1∶2·50 and 1∶2·75 respectively, were employed. Experimental evidence showed that a combustion wave featuring a spinning reaction zone can be observed. When the powder compacts are from Mo∶1·25Si to Mo∶1·75Si, the combustion temperature and the propagation velocity of combustion wave increase with increasing silicon in the sample, and the combustion products are composed of MoSi₂, Mo₅Si₃ and Mo. However, when the powder compacts are from Mo∶2·25Si to Mo∶2·75Si, the combustion temperature and the propagation velocity decrease rapidly as the silicon in the compact increases, and the combustion products are composed of MoSi₂ and Si. The sample with Mo/Si = 1∶2·00 possesses the highest combustion temperature (1628·9 K) and propagation velocity (3·13 mm s⁻¹). A single-phase MoSi₂ is synthesised by the Mo/Si = 1∶2·00 sample.